Sand fracturing apparatus and method

ABSTRACT

A sand fracturing machine for breaking coarse grain of sand into smaller grains. The machine includes an open topped container having a bottom wall with circular openings therethrough. Rods of steel or other suitably hard material are located in the box and are supported by the bottom wall. Sand containing grains of many different sieve sizes is introduced into the container through its open top which falls on top of the rods. A vibration mechanism connected to the container is operative to vibrate the container in a substantially vertical direction. The sand sifts downwardly between the vibrating rods and out through the openings in the bottom wall of the container. As the larger grains pass between the vibrating rods, however, they are fractured by the rods to create smaller mid-size grains while the smallest grains sift between the rods unaffected. Consequently, the machine is operative to produce a sand aggregate with a different grain size distribution from that of the sand put into it which principally has a greater percentage of mid-size grains than found in the sand placed into the machine.

United States Patent 11 1 1111 3,870,238 Sellars Mar. 11, 1975 SANDFRACTURING APPARATUS AND Primary Examiner-Roy Lake METHOD AssistantE.\'aminerE. F. Desmond [75] Inventor: George L. Sellars, Cincinnati,Ohio Attorney Agent or Fmn w0od Herron & Evans [73] Assignee: DravoCorporation, Pittsburgh, Pa. [57 ABSTRACT [22] Filed: Feb. 22, 1973 Asand fracturing machine for breaking coarse grain of sand into smallergrains. The machine includes an [211 App! 334695 open topped containerhaving a bottom wall with circular openings therethrough. Rods of steelor other [52] US. Cl 241/27, 241/DIG. 10, 241/175 suitably hard materialare located in the box and are [51] Int. Cl. B02c 17/14 supported by thebottom wall. Sand containing grains [58] Field of Search 241/D1G. 10,27, 63, 175; of many different sieve sizes is introduced into the 106/97container through its open top which falls on top of the rods. Avibration mechanism connected to the [56] References Cited container isoperative to vibrate the container in a n- STATES PATENTS substantiallyvertical direction. The sand sifts downwardly between the vibrating rodsand out through the 'f 2392 openings in the bottom wall of thecontainer. As the larger grains pass between the vibrating 'rods,.how-

FOREIGN PATENTS OR APPLICATIONS ever, they are fractured by the rods tocreate smaller 485,969 5/1938 Great Britain 241/175 mid-size grainswhile the smallest grains sift between OTHER PU BLICATIONS Nordberg,Bror, Sand for Wolf Creek Dam, Rock Products, Dec. 1968, p. 102.

the rods unaffected. Consequently, the machine is operative to produce asand aggregate with a different grain size distribution from that of thesand put into it which principally has a greater percentage of mid-sizegrains than found in the sand placed into the machine.

9 Claims, 6 Drawing Figures SAND FRACTURING APPARATUS AND METHODBACKGROUND OF THE INVENTION This invention relates to a sand fracturingmachine for producing a sand aggregate having a more uniform grain sizedistribution than is normally found in sand removed directly from gravelpits and especially including more grains in the mid sieve size range.

In the field of concrete manufacture, it is highly desirable to have asand aggregate which includes sand grains of varying sizes. Furthermore,it is equally desirable to have a distribution of grain sizes within theaggregate which approximates a uniform distribution whenever a concretewith a very fine finish is desired.

Typically, however, sands removed from most gravel pits contain unevendistributions of grain sizes. Specifically, the percentage of sandgrains which are large in size (sieve sizes greater than No. 30)frequently comprises a large proportion of the raw aggregate. Similarly,sand having a grain size which is very small (sieve sizes less than No.50) also comprises a very large percentage of the raw material removedfrom such gravel pits. Consequently, the percentage of sand grains inthe mid-size range comprises a lower percentage of the aggregate than isdesirable in fine finish concrete. As a consequence, the typical rawsand removed from most gravel pits has a very uneven distribution ofgrain sizes and is especially lacking in mid-sized grains. When suchsand aggregates are used in concrete, for example, the lack of mid-sizedgrains precludes a substantially uniform mixing of the sand aggregatewith the sand binder so that the surface of'the concrete after thebinder sets is not very smooth. As such, the typical raw sand from suchgravel pits is not well suited for use in concrete where a very smoothsurface is desired.

In an attempt to overcome the problem associated with the lackofmid-sized grains in typical sand, various types of grinding andcrushing machines have been used. However, these machines have producedtoo large a percentage of fines and have not given the uniformdistribution of grain sizes desired in the end product. The grindingaction has not been selective in the sense that the mid range of grainsizes is preserved. All grains of the sand have been subjected tocrushing action. Thus, these grinding machines have not been successfulin providing an aggregate with a greater percentage of mid-size grainsof sand than is normally found in sand removed directly from a gravelpit.

In view of the foregoing difficulties in providing sand aggregateshaving the desired grain size distribution, it is a primary objective ofthis invention to provide a method and apparatus suitable for producingfrom available sand aggregates a new aggregate which has a grain sizedistribution suitable for use in fine finish concrete.

It is a further objective of this invention to provide a sand fracturingmachine for breaking large sized grains in available aggregates toproduce at its output a new aggregate having a significantly higherpercentage of grains in the midsize range than in the aggregateintroduced into the machine.

It is still a further objective of this invention to provide a sandfracturing machine that breaks the large sized grains in a typical sandaggregate to produce an aggregate at its output having a significantlyhigher percentage of mid-sized grains without significantly increasingthe percentage of small sized grains in the aggregate.

These and other objects of this invention are generally provided by thesand fracturing machine described herein. The machine includes an opentopped container which has an apertured bottom wall to permit outputsand to pass freely therethrough. The machine includes a plurality ofelongated, cylindrical rods which are disposed within the open toppedcontainer with at least some of the rods being directly supported frombelow by the apertured bottom wall. The box itself is supported by avibrating support which is operative to vibrate the lower portion of thebox in a substantially vertical direction. Raw sand from a typicalgravel pit is introduced into the machine and the vibrator turned on. Asthe open topped container is vertically vibrated, the sand siftsdownwardly through the vibrating rods and ultimately passes out throughthe bottom apertured. wall. The vibration of the rods is operative tobreak large grains of sand between the rods as the sand sifts downwardlytherethrough while passing the smaller grains. Since the broken grainshave a smaller size than the original grains, the apparatus is operativeto produce a large number of mid-sized grains at its output by crackingthe larger sized grains of the input aggregate into smaller grains.

To produce a sand aggregate which has a substantially uniformdistribution of grain sizes throughout, the output sand from the machineis then combined with a typical raw sand aggregate from a gravel pit toproduce a sand aggregate with a greater percentage of sand grains in themid grain size than in the original gravel pit aggregate withoutsignificantly changing the percentage of sand grains in either of thelarge or small grain size.

These and other objects, advantages and features of this invention willbecome more clear from the following detailed description of a preferredembodiment taken in connection with the drawings'which form a part ofthe original disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partially cut-awayperspective view of the sand fracturing machine of this invention;

FIG. 2 is a vertical sectional view along the longitudinal axis of themachine;

FIG. 3 is a vertical sectional view taken along another axis of themachine;

FIG. 4 is a vertical sectional view taken through a segment of thebottom wall of the machine;

FIG. 5 shows schematically the operation of the machine;

FIG. 6 shows schematically various sand aggregate distributions.

DETAILED DESCRIPTION Briefly, the present invention relates to a sandfracturing apparatus which includes an open topped container forreceiving sand aggregate from a typical gravel pit. This open toppedcontainer includes a bottom apertured wall with openings therethrough topermit output sand to freely pass therethrough. Disposed within the opentopped container are a plurality of elongated rods generally made of avery hard material such as steel which are disposed with theirlongitudinal axis substantially parallel to the bottom wall and with atleast some of these rods resting directly on the bottom wall. A vibratoris provided to vibrate the open topped container and the rods disposedtherein in a substantially vertical direction to thereby permit the sandwhich is introduced into the open topped container to sift downwardlythrough the vibrating rods and eventually fall through the apertures inthe bottom wall. By selecting the rate of vibration, the size and numberof rods and even the size of the apertures in the bottom wall, thedistribution of grain sizes in the sand aggregate leaving the machinecan be significantly changed from the distribution of grain sizes in thesand that is introduced.

The sand that falls through the apertured bottom wall of the containermay itself be used for certain types of concrete, however, for extremelysmoothed surfaced concretes the output sand is combined normally withsand directly from the gravel pit to provide a combined sand aggregatewith a more uniform distribution of sand grain sizes.

Referring now to FIG. 1, a preferred sand fracturing machine is shown inperspective and partially cut-away. The machine is generally supportedon a rigid support frame which typically comprises a number of steelbeams welded or otherwise rigidly connected together to form a rigidsupport for the movable portions of the apparatus. Rigidly mounted onand supported by the support frame 10 is a drive motor 12 which providesthe motive power for the vibratory motion of the machine. The motor 12is typically an electric motor having a rotary drive shaft 14 to which apulley 16 is affixed. For the preferred embodiment of this invention,the pulley 16 includes two circumferential beltengaging grooves so thatthe rotary drive power can be transmitted via two drive belts 18 fromthe pulley 16 to the driven pulley 20. A belt shroud 22 supported by thesupport frame 10 is provided to protect workers from possible breakageof a drive belt 18 as well as to protect workers from accidentallycoming into contact with the rotatingpulleys l6 and or the moving drivebelts 18.

In a preferred embodiment of this invention, the motor 12, the pulley l6and the driven pulley 20 are arranged so that the driven pulley 20 willrotate at approximately 510 revolutions per minute when driven by themotor 12. It will be clear to those of skill in the art, however, thatdifferent rotary speeds of the driven pulley 20 may be employed byapparatus of the type characterized by this invention to thereby providedifferent vibrational frequencies.

The driven pulley 20 is affixed to a drive shaft 24 so that both thedriven pulley 20 and the drive shaft 24 have a common axis of rotation26. The drive shaft 24 is rotatably mounted at one end 25 to the supportframe 10 by a bearing 28 and a bearing support 30 which is rigidlyaffixed to the support frame 10. The other end 32 of the drive shaft 24engages a second bearing 34 supported by a second bearing support 36which itself is rigidly affixed to the support frame 10. This end 32 ofdrive shaft 24 has an axis of rotation 38 which, if extended, coincideswith the axis of rotation 26 for the other end 25 of drive shaft 24.Disposed between the ends 25, 32 of the drive shaft 24 is a supportshaft 40 which comprises a solid cylindrical body preferably formed ofsteel or other hard and strong material and has an axis of rotation 42.The support shaft 40 is rigidly connected to the drive shaft ends 25 and32 by welding or other suitably strong connection in a manner so thatthe axis 42 of the support shaft 40 is displaced from though parallel toaxis 26 and 28. Consequently, the support shaft 40 is eccentricallyconnected to the drive shaft ends 25 and 32 so that when the drive shaft24 is driven in rotary motion about the axes of rotation 26 and 38, thesupport shaft 40 rotates eccentri' cally about the drive shaft axes. Inthe preferred embodiment of this invention, the axis 42 of the supportshaft 40 is displaced from the drive shaft axes 26, 38 by approximatelyone-quarter inch.

Rotatably secured to the shaft 40 is an open topped container whichincludes two end walls 44 which are disposed in parallel spaced relationand supported on the support shaft 40 by two bearings 46 which arelocated in the end walls 44 substantially near the uppermost partthereof. The end wall 44 in the preferred embodiment of this inventioncomprise a rigid planar body of steel or rigid strong materialapproximately one-half inch thick.

Disposed between the two end walls 44 are two side walls 45 formed ofthe same material as the end walls 44 and located between the end walls44 in parallel spaced relation to thereby provide a container whoseupper opening and lower opening is substantially rectangular in shape.Removably mounted to the lowermost edges of the end walls 44 and theside walls 45 is an apertured bottom wall 48 which includes a pluralityof apertures 50 extending completely through the bottom wall 48. Likethe side walls 45 and the end walls 44, the bottom wall 48 is preferablyformed of a strong planar material, such as a one-half inch steel plate,through which the apertures 50 have been made. The bottom wall 48 ispreferably removably attached to the end walls 44 and the side walls 45by a plurality of nuts and bolts 52 which secure the bottom walls 48 tothe outwardly extending flanges 54 of the end walls 44 and the sidewalls 45. Since the bottom wall 48 is removably attached to the endwalls 44 and the side walls 45, the bottom wall 48 may be readilyremoved and replaced by another bottom wall having apertures ofdifferent size and number from the bottom wall removed from the opentopped containers.

Extending downwardly from the apertured bottom wall 48 are a pluralityof rib-like bottom wall strengtheners 56 which are preferably made ofsteel or other suitably strong material, and are welded or otherwiserigidly affixed at their upper end to the lower surface of the aperturedbottom wall 48. Disposed at opposite ends of support ribs 56 aresupporting end walls 58 which include outwardly extending flanges 60 injuxtaposition to the flanges 54 through which the nuts and bolts 52 alsoextend to thereby rigidly secure the support walls 58 to the side walls45 and end walls 44. It will be clear to those of skill in the art thatthe support ribs 56 and the support end walls 58 may be formed innumerous other ways while still maintaining adequate support for thebottom wall 48.

Referring briefly to FIG. 4, the apertures 50 in the bottom walls 48 areshown in greater detail. Each of these apertures 50 includes an upperopening having a circular diameter 62 and a lower opening having acircular diameter 64. Sloping side walls 66 connect the upper openingwith the lower opening. Since the upper opening has a diameter 62 whichis preferably smaller than the lower diameter 64, the aperture 50through the bottom wall 48 is frustoconical in shape and advantageouslyprovides an aperture in the bottom wall 48 through which sand grainswill readily pass and. as is well known in the art, the aperture 50shaped as de scribed will prevent sand grains from becoming wedgedtherein because the upper opening has a smaller diameter than the loweropening.

Returning now to FIGS. l-3, the apparatus of this invention includes aplurality of elongated rods 68 located at the bottom of the open toppedcontainer. The longitudinal axes of each rod is disposed substantiallyparallel to the bottom wall 48. Additionally, the diameter of these rods68 is selected so that at least some of the rods 68 are resting on thebottom wall 48 and that some other rods 68 are supported above thebottom wall 48 in resting engagement with other rods 68. In onepreferred. embodiment of this invention, the rods 68 are formed of solidsteel and preferably Rychrome steel manufactured by the Ryerson SteelCompany. Each rod 68 has a length substantially equal to but slightlyless than the distance between the end walls 44, thereby providing alayer of rods 68 located at the bottom of the open topped containerwhich, as will become more clear later, is operative to crack largersand grains into smaller sand grains while permitting smaller grains toflow freely therethrough and ultimately through the apertures 50 in thebottom wall 48.

Rotatably mounted to each end wall 44 at a point generally shown as 70is the tie rod 72. At the opposite end of each tie rod 72 from the point70 is a similar rotary connection 74 for joining each tie rod 72 to asupport bracket 76 which is rigidly affixed to the support frame 10. Thetie rod 72 is provided to restrain the movement of the open toppedcontainer in a horizontal or sidewise direction indicated generally bythe doubleheaded arrow 78 at the lowermost portion thereof, whilepermitting substantially vertical movement in the direction indicated bythe substantially vertical doubleheaded arrow 80. As such, the lowerportion of the open topped container which includes the end walls 44,the side walls 45, and the bottom wall 48, is constrained tosubstantially vertical movement near the lowermost portions thereof.

In operation mechanically, the apparatus shown in FIGS. l-3 performs inthe following manner. The electric motor is operative to rotate thepulley 16 about the drive axis 14. The drive belts 18, being inoperative engagement with the pulley l6 and the pulley 20, transmit therotary motion from the motor 12 to the driven pulley 20. This rotarymotion of the driven pulley 20 is transmitted to the connected driveshaft 24 to thereby move the support shaft 40 in an eccentric manner.The support shaft 40 is rotatably mounted to the end walls 44 of theopen topped container by the bearings 46. Consequently, when the motor12 is turned on, the upper portion of the open topped container iseccentrically moved about the axes of rotation 26, 38. Since the lowerportion of the open top container is restrained by the tie rod 72, thelower portion of the open topped container is vibrated substantially ina vertical direction as indicated by the arrow 80 to thereby move up anddown the lower portion of the open topped container by an amountapproximately equal to one-half inch in the preferred embodiment of thisinvention.

Referring again to FIGS. l-3, a cylindrical steel support rod protectingshroud 81 is provided to protect the support shaft 40 and is joined atopposite ends to the end walls 44. This shroud 81 is primarily providedto shield the rotary support shaft 40 from excessive wear due to contactwith sand as it is introduced into the open topped container whichcomprises the end walls 44, the side walls 45, and the bottom wall 48'.The shroud 81 also serves to protect the bearings 46 from contact withthe sand as well. In addition, an outwardly extending flange 79 isprovided along the edges of each end wall 44 to prevent contact withrotary parts as well as to serve as a measure of protection for thebearings 46 from contact with sand.

Since there is an eccentric connection between the drive shaft ends 25and 32 with the support shaft 42, counterweights 82 are disposed onthese ends 25 and 32 to assure that the vibratory motion imparted to theopen topped container is not transmitted through the drive shaft to theframe 10. Again, as a safety measure. protective shrouds 83 are providedto prevent accidental contact with the rotating counterweights 82 aswell as to provide some measure of protection of these rotating partsfrom sand or other foreign objects.

Having described the apparatus and its mechanical operation, theusefulness of this apparatus is best described with reference to FIG. 5.The operator will normally introduce an amount of sand into the opentopped container so that the sand covers the rods 68. When the motor 12is activated, the open topped container, the rods 68 and sand vibratedto thereby permit the sand located above the rods 68 to gradually shiftdownwardly between the rods 68. This is shown in FIG. 5 wherein aplurality of sand grains are shown diagrammatically at and include smallgrains 92 and a larger grain 94. As the sand sifts between the vibratingrods 68, the larger grains 94 will become located between the rods 68.As the vibrating rods come together, they will crack larger grains ofsand disposed therebetween but will not crack the smaller grains becausethe larger grains separate the rods 68 preventing contact thereby withsmaller grains. Since the larger grains 94 are cracked, however, thenumber of sand grains in the mid-size range which fall through theapertures in the bottom wall 48 is increased because the crackingprocess tends to produce from larger grains a large number of grains inthe mid-size range.

The usefulness of this sand fracturing machine is best shown inconnection with FIG. 6. For various applications, the sand aggregaterequired for a particular job is often defined according tospecifications. Typical specifications for a very fine finish concreteis shown in FIG. 6 in the shaded region. The sand aggregate for thisconcrete ideally should have a grain size distribution such that, forexample, all of the sand in the aggregate will be passed by a /8 inchsieve while from 0 to 4 percent of the aggregate should be passed by aNo. 200 sieve. For other sieve sizes, the range in which the aggregateshould fall is shown, as indicated earlier, by the shaded area. Inaddition, it has been found to be highly desirable to have grains ofsand in the mid-size range, i.e., those in the No. 30 to No. 50 sievesize fall well within the acceptable range. Experience has shown,however, that normal gravel pit outputs are especially lacking in sandgrains in this particular range of grain sizes. This indeed is shown bythe curve labeled input. This curve shows a specific sample of a typicalgravel pit output and for the No. 30 sieve size, the percentage ofaggregate passing through the No. 30 sieve.

size is very close to the lower limit of the specifications and, whenthe sieve size is decreased to that ofNo. 40,

the percentage passing through the No. 40 sieve is less than called forby the specifications. As a consequence,

the sand from this particular gravel pit does not meet the requiredspecifications for fine finish concrete and something must be done tothe gravel aggregate to make it conform.

In the past, one approach to changing the distribution of grain sizes inthe aggregate has been to first size the sand using various sift sizesand then combine the separated sands to produce the desireddistribution. Obviously, this particular approach is inefficient andcostly.

To overcome the prior art deficiencies in producing a sand with anaggregate content which fully meets the specifications, a sandfracturing machine of the type disclosed is very useful. In FIG. 6, forexample, a curve labeled output is drawn for the aggregate content atthe output of the machine when a sand with the aggregate content shownfor the input curve is put into this machine. It should be noted thatthe curve representing the aggregate content for the sand crusher outputfalls within the specifications except for the grain sizes between No.10 and No. 4. However, in the critical midsize range between No. 30 andNo. 50, the output of the sand crusher is well within and substantiallyat the middle of the specification range.

The sand crusher output itself may even be acceptable for use in smoothsurfaced concrete because the deviation in the grain size contentbetween No. 10 and No.4 is not very significant and, furthermore, thisdeviation occurs for a less critical grain size. On the other hand, asand with an aggregate content fully meeting specifications can veryeasily be produced by combining on, a one-for-one basis, the sandcrusher output with the uncrushed gravel pit sand. By such a combinationon a one-for-one basis, the actual aggregate curve would lie midwaybetween the input and the output curves which will lie completely withinthe specifications. As such, for the particular gravel pit sandaggregate sample shown in FIG. 6, and for the results achieved with themachine, an operator can readily modify the aggregate composition of thesand so that a sand meeting fine finish concrete specifications isavailable.

It will be clear to those skilled in the art that the foregoingdiscussion has been made with particular emphasis on using the sandbreaking apparatus with a sand having a known aggregate composition andthat the method of operation is equally applicable to sands havingdiffering aggregate compositions. For each application, the aggregatecomposition of the sand before and after crushing must be known so thatthe proper quantities of each type of sand (treated or untreated) can becombined to form a combined aggregate with the desired distribution ofthe sand grain sizes.

While the foregoing description has been made with particular emphasison a preferred sand fracturing machine, it will be clear to thoseskilled in the art that certain modifications in form only may be madewithout departing from the spirit and scope of this invention. Forexample, the apparatus of the present invention might readily bemodified to change the vibrating mechanism so that the open topped sandreceiving container would be vibrated in vertical direction by othermeans other than those specifically shown in FIGS. 1-3. Indeed, someform of eccentric drive means might be located beneath the sandreceiving container to vibrate the box only in a vertical direction.

While the preferred embodiment of this invention utilizes steel rods ofapproximately 2 inches in diameter, it will be clear to those of skillin the art that rods of different or even differing diameters may alsobe used with the same advantageous results achieved by the presentinvention. By using a different number of rods having either differentor differing diameters, the actual results of the operation on a giveninput sand aggregate is somewhat different from the output with otherrods. As such, the operator may, if he so chooses, vary the rod diameterin order to vary the aggregate composition of the sand output, therebyproviding a sand aggregate with a grain sized distribution preferablymore approximating those of a desired specification. It is equally clearthat the bottom aperture wall, being removably attached to the end wallsand the side walls, may also be changed to provide some correspondingchanges in the aggregate distribution at the output.

A further modification is to vary the vibration frequency to therebyincrease or decrease the vibration rate on the rods which has an effecton the overall grain size distribution at the output of the machine.

The foregoing and other modifications in form only may be readily madeby those of skill in the art without I departing from the spirit andscope of this invention as defined by the following claims.

What is claimed is:

1. A sand fracturing machine comprising, in combination:

an open topped container with a horizontal bottom wall with aperturestherethrough and vertical side walls, said apertures being shaped toprevent sand grains from becoming wedged therein and large enough topass substantially all the sand aggregate introduced into saidcontainer, said container being mounted for movement substantially onlyin a vertical direction;

a plurality of elongated rods disposed within said container with thelongitudinal axis of each rod being disposed substantially parallel tosaid bottom wall, said rods being unattached to said container and freeto move in a vertical direction; and

a vibrator apparatus operably connected to said container to vibratesaid container and rods in a generally vertical direction wherein thelarger grains of sand in a sand aggregate placed into said open toppedcontainer are fractured by the vibrating rods to produce a greaterpercentage of mid-size sand grains in the output sand aggregate of themachine than is contained in sand aggregate introduced into the machinewithout substantially increasing the percentage of fine sand grains inthe output sand aggregate.

2. The machine according to claim 1 wherein each of said apertures insaid bottom wall are frustoconical in shape with its smaller openingbeing disposed upwardly to communicate with said container.

3. The machine according to claim 1 wherein at least some of said rodsare supported from below by said bottom wall and at least some otherrods are supported from below by other rods.

4. The machine according to claim 1 wherein said vibrator means includesan eccentric drive connected to said container near the top of saidcontainer, said eccentric drive being operative to move the upperportion of said container in eccentric motion.

5. The machine according to claim 4 additionally including a motionrestraint member connected to the lower portion of said container torestrain horizontal motion while permitting vertical motion of the lowerportion of said container.

6. The machine according to claim 1 wherein said bottom wall isremovably attached to said container.

7. A sand fracturing machine comprising, in combination:

an open topped container for receiving sand to be fractured, saidcontainer including a horizontal bottom wall with apertures therethroughlarge enough to permit substantially all the sand aggregate introducedinto said container to freely pass therethrough without becoming wedgedtherein, said container including vertical side walls;

a plurality of elongated rods disposed within said container with thelongitudinal axis of each rod being disposed substantially parallel tosaid bottom wall, at least some of said rods resting on said bottomwall, said rods being unattached to said container and free to move in avertical direction;

a support shaft rotatably mounted to said container near the upperopening therefor;

a support frame;

a pair of drive shafts with common axes of rotation rotatably mounted tosaid frame and eccentrically connected a vibrator apparatus operablyconnected to said container to vibrate said container and rods in agenerally vertical direction wherein the larger grains of sand in a sandaggregate placed into said open topped container are fractured by thevibrating rods to produce a greater percentage of mid-size sand grainsin the output sand aggregate of the machine than is contained in sandaggregate introduced into the machine without substantially increasingthe percentage of fine sand grains in the output sand aggregate.

8. The sand fracturing machine according to claim 7 wherein said opentopped container includes two end walls in parallel spaced relation andtwo side walls also inparallel spaced relation, said side walls and endwalls being joined together to form the sides of said container, saidcontainer also including said bottom wall which is removably attached tothe lower edges of said end and said side walls.

9. A method of modifying the percentage of sand grains in the mid grainsize of a sand aggregate contain- ,ing relatively few sand grains in themid grain size comprising the steps of:

introducing a quantity of raw sand aggregate containsize grains thanfound in the raw aggregate.

1. A SAND FRACTURING MACHINE COMPRISING, IN COMBINATION: AN OPEN TOPPEDCONTAINER WITH A HORIZONTAL BOTTOM WALL WITH APERTURES THERETHROUGH ANDVERTICAL SIDE WALLS, SAID APERTURES BEING SHAPED TO PREVENT SAID GRAINSFROM BECOMING WEDGED THEREIN AND LARGE ENOUGH TO PASS SUBSTANTIALLY ALLTHE SAND AGGREGATE INTRODUCED INTO SAID CONTAINER, SAID CONTAINER BEINGMOUNTED FOR MOVEMENT SUBSTANTIALLY ONLY IN A VERTICAL DIRECTION; APLURALITY OF ELONGATED RODS DISPOSED WITHIN SAID CONTAINER WITH THELONGITUDINAL AXIS OF EACH ROD BEING DISPOSED SUBSTANTIALLY PARRALLEL TOSAID BOTTOM WALL, SAID RODS BEING UNUNATTACHED TO SAID CONTAINER FREE TOMOVE IN A VERTICAL DIRECTION; AND A VIBRATOR APPARATUS OPERABLECONNECTED TO SAID CONTAINER TO VIBRATE SAID CONTAINER AND RODS IN AGENERALLY VERTICAL DIRECTION WHEREIN THE LARGER GRAINS OF SAND IN A SANDAGGTEGATE PLACED INTO SAID OPEN TOPPED CONTAINER ARE FRACTURED BY THEVIBRATING RODS TO PRODUCED A GREATER PERCENTAGE OF MID-SIZE SAND GRAINSIN THE OUTPUT SAND AGGREGATE OF THE MICHINE THAN CONTAINED IN SANDAGGTEGATE INTRODUCED INTO THE MACHINE WITHOUT SUBSTANTIALLY INCREASINGTHE PERCENTAGE OF FINE SAND GRAINS IN THE OUTPUT SAND AGGREGATE.
 1. Asand fracturing machine comprising, in combination: an open toppedcontainer with a horizontal bottom wall with apertures therethrough andvertical side walls, said apertures being shaped to prevent sand grainsfrom becoming wedged therein and large enough to pass substantially allthe sand aggregate introduced into said container, said container beingmounted for movement substantially only in a vertical direction; aplurality of elongated rods disposed within said container with thelongitudinal axis of each rod being disposed subsTantially parallel tosaid bottom wall, said rods being unattached to said container and freeto move in a vertical direction; and a vibrator apparatus operablyconnected to said container to vibrate said container and rods in agenerally vertical direction wherein the larger grains of sand in a sandaggregate placed into said open topped container are fractured by thevibrating rods to produce a greater percentage of mid-size sand grainsin the output sand aggregate of the machine than is contained in sandaggregate introduced into the machine without substantially increasingthe percentage of fine sand grains in the output sand aggregate.
 2. Themachine according to claim 1 wherein each of said apertures in saidbottom wall are frustoconical in shape with its smaller opening beingdisposed upwardly to communicate with said container.
 3. The machineaccording to claim 1 wherein at least some of said rods are supportedfrom below by said bottom wall and at least some other rods aresupported from below by other rods.
 4. The machine according to claim 1wherein said vibrator means includes an eccentric drive connected tosaid container near the top of said container, said eccentric drivebeing operative to move the upper portion of said container in eccentricmotion.
 5. The machine according to claim 4 additionally including amotion restraint member connected to the lower portion of said containerto restrain horizontal motion while permitting vertical motion of thelower portion of said container.
 6. The machine according to claim 1wherein said bottom wall is removably attached to said container.
 7. Asand fracturing machine comprising, in combination: an open toppedcontainer for receiving sand to be fractured, said container including ahorizontal bottom wall with apertures therethrough large enough topermit substantially all the sand aggregate introduced into saidcontainer to freely pass therethrough without becoming wedged therein,said container including vertical side walls; a plurality of elongatedrods disposed within said container with the longitudinal axis of eachrod being disposed substantially parallel to said bottom wall, at leastsome of said rods resting on said bottom wall, said rods beingunattached to said container and free to move in a vertical direction; asupport shaft rotatably mounted to said container near the upper openingtherefor; a support frame; a pair of drive shafts with common axes ofrotation rotatably mounted to said frame and eccentrically connected tosaid support shaft at opposite ends thereof for providing eccentricmotion to said support shaft relative to said support frame when saiddrive shafts are rotated; means for rotating at least one of said driveshafts; and at least one tie rod pivotally connected at one end to saidsupport frame and pivotally connected at the other end to the lowerportion of said container said tie rod being operative to restrainhorizontal motion of the lower portion of said container whilepermitting substantially vertical motion when said drive means isoperative to rotate said drive shaft.
 8. The sand fracturing machineaccording to claim 7 wherein said open topped container includes two endwalls in parallel spaced relation and two side walls also in parallelspaced relation, said side walls and end walls being joined together toform the sides of said container, said container also including saidbottom wall which is removably attached to the lower edges of said endand said side walls.